1. Field of the Invention
The present invention relates generally to the composition of photoluminescence polymers, the process for making and the methods of use.
More particularly, the present invention relates to the composition of novel photoluminescence polymers that provide extremely long afterglow characteristics. The novel composition contains known moisture sensitive photoluminescence pigments and a polyvinyl alcohol polymer which is water soluble, and which imparts moisture stability to the photoluminescence pigment. The resulting photoluminescence polymers are capable of repeating the light-absorption/light-emission cycle numerous times.
Further, the present invention relates to the method of preparing the novel photoluminescence polymers by combining photoluminescence pigments and polyvinyl alcohol under specific conditions.
Additionally, the present invention relates to the methods of using of these photoluminescence materials.
2. Description of the Prior Art
Products providing glow in the dark or fluorescence properties are well known in many consumer applications. These products are used in applications such as clothing, toys, novelty items, fire protection products, emergency products, safety products, sporting goods such as diving sticks, plastic tubing, stationary, signs, military applications, synthetic leathers, construction uses such as bridges and monuments, outdoor decoration and the like. Generally, when a phosphorescent pigment is incorporated in a synthetic resin, the phosphorescent pigment is not easily dispersed uniformly in the synthetic resin and the resultant phosphorescent synthetic resin inevitably emits light of uneven color.
One well-known method for providing glow in the dark or fluorescence properties is zinc sulfide phosphorescent phosphor (ZnS:Cu). Zinc sulfide phosphorescent phosphor is decomposed by ultraviolet radiation in the presence of moisture and thus blackens or reduces the luminance thereof Therefore, it is difficult to use this phosphorescent phosphor in fields where it is placed outdoors and exposed to a direct sunlight.
Another well-known method for providing glow in the dark or fluorescence properties is found by combining zinc sulfide with radioactive substances. The radioactive substance, however, has the problem that it must be handled under a rigid standard of safety control and, moreover, the disposal of the waste arising therefrom incurs great expense. Further, when the phosphorescent pigment is incorporated into a synthetic resin in an amount sufficient to increase the fluorescence properties, the problem ensues that the resultant phosphorescent resin will not easily acquire sufficient strength necessary for a resinous product.
Another well-known method for providing glow in the dark or fluorescence properties is sulfide phosphorescent phosphors. Examples of sulfide phosphorescent phosphors include CaS:Bi (which emits light of violet blue), CaSrS:Bi (which emits light of blue), ZnS:Cu (which emits light of green) and ZnCdS:Cu (which emits light of yellow or orange). However, any of these sulfide phosphorescent phosphors is chemically unstable and shows degraded light resistance, i.e., it suffers from problems that must be solved for practical use.
Other methods for providing glow in the dark or fluorescence properties are disclosed in U.S. Pat. Nos. 5,424,006 and 5,686,022. Both the 5,424,006 and the 5,686,022 patents disclose phosphorescent phosphors which can be utilized both indoors and outdoors as a nighttime display and show extremely long afterglow characteristics. However, these phosphorescent phosphors must be incorporated into chemical hydrocarbon solvent-based systems as moisture or aqueous systems adversely affect them. These references are incorporated by reference in their entirety.
Yet another method for providing glow in the dark or fluorescence properties is an alkaline earth metal aluminate oxide europium doped which has the chemical composition of SrO.circle-solid.SrAl.sub.4 O.sub.7-Eu and is marketed under the trade name of NightLight20. NightLight20 or SrO.circle-solid.SrAl.sub.4 O.sub.7-Eu is a commercially available phosphorescent pigment. However, similar to the phosphorescent phosphors disclosed in the 5,424,006 and 5,686,022 patents, Nightlight20 is adversely affected by moisture or aqueous systems and therefor are only suitable for blending with oil based materials.
U.S. Pat. No. 5,665,793 discloses a composition where phosphorescent phosphors, such as those in the 5,424,006 and 5,686,022 patents, are combined with polyurethane resins which are water soluble, and which imparts moisture stability to the phosphorescent phosphors. As a result, this novel composition when used in water-based highway paints imparts an extended road surface life, and is environmentally friendly because it does not contaminate the surrounding environment with organic hydrocarbon products via vaporization or runoffs. However, these phosphorescent phosphor polyurethane resins are not moldable or formable as in the present invention.
U.S. Pat. 5,607,621 discloses a composition where phosphorescent phosphors, such as those in the 5,424,006 and 5,686,022 patents, are combined with synthetic resins to provide a phosphorescent synthetic resin material that possesses ample strength enough for enabling a formed article made of this material to withstand repeated use. However, these phosphorescent synthetic resin materials are not water-soluble.
U.S. Pat. Nos. 5,244,429 and 4,634,395 disclose gas barrier coating and coated elastomeric toy balloons. Although not relating to the photoluminescence art, the coatings described herein are polyvinyl alcohol based solutions. These solutions provide neither photoluminescence nor the ability to be molded. These references are incorporated by reference in their entirety.
The prior art as disclosed by the 5,424,006 and 5,686,022 patents as well as an analysis of the disclosures of Nightlight 20 teach away from using these moisture sensitive pigments in aqueous systems such as polyvinyl alcohol. Although the 5,665,793 patent discloses using these moisture sensitive pigments with a water-soluble polyurethane resin, the resulting products are not moldable. Accordingly, a continuing need exists for a moldable, non-toxic, non-radioactive, environmentally friendly photoluminescence polymers which do not require solvent based systems and that provides a uniform, bright afterglow for extended periods of time and are usable both indoors and outdoors.